Integrated circuit devices have many applications in industry today. In order to provide for proper operation, however, they must be tested to ensure quality within acceptable limits. Such testing and burn-in of integrated circuit devices typically require that the devices be actuated by engagement of leads of a device with corresponding contacts of a test socket, the contacts of the test socket, in turn, being electronically communicated with terminals of a printed circuit board of a test apparatus. It is desirable that such integrated circuit devices can be tested in both manual and automated test equipment. In methods known in the art, "pick and place" handling employs the modification of existing manual test sockets in order to construct dedicated test sockets which interface with a tester
Sockets of this type, typically, include a socket housing, the housing including an array of compliant contacts. Further, the socket includes a cover assembly which is, typically, hinged at one edge of the socket housing. The cover is latched, when a device is in the test socket, at an edge of the socket housing opposite that of the hinging.
The integrated circuit devices align within the socket housing by various means. Such means serve to guide the leads of the device into engagement with corresponding contacts within the test socket cavity.
Test/burn-in sockets must be temperature stable; they must be capable of withstanding temperatures between -65.degree. and +165.degree. Celsius. Such extreme temperatures must be able to be withstood for hundreds, if not thousands, of hours of test time, and such endurance must be without any appreciable degradation of operational capability.
Further, it is desirable that a test socket be durable As such, it would be able to withstand the repeated insertion of integrated circuit ,devices for test. Typically, a life cycle of in excess of ten thousand insertions would be expected.
A number of factors must be taken into consideration when considering such a test socket. First, a contact at the test socket housing must include a tip extending upwardly for engagement by a corresponding lead of the device to be tested. The contact is profiled appropriately for interfacing with the device lead. If not appropriately profiled, engagement of the contact tip by the device lead will not effect desired wiping action.
Another factor which must be considered is the compliance of the contact array. Typically, all distal ends of the integrated circuit device leads are not co-planar. The compliance of the test socket housing contacts takes into account this lack of co-planarity. Consequently, as a device is moved so that leads thereof are brought into engagement with corresponding contacts of an array, an efficient amount of force can be applied to each of the device leads to ensure that a good, low contact resistance interface will be achieved.
In the prior art, contacts in such test sockets as being discussed herein, are generally formed with cantilevered arms. Tips of such contacts extend downwardly into the test socket housing. It is within the socket housing that the tips of the contacts are held.
A further consideration to which attention must be given is the manner in which contacts are held and aligned within the housing. It must be ensured that the contacts also serve to be in electronic communication with a printed circuit board of a tester. In the prior art, this is accomplished by employment of an extension of a contact which is formed as a small rectangular or square pin. These square or rectangular pin ends are then inserted into holes formed in the printed circuit board. They are soldered in place.
One proposed solution of the prior art employs a ridge formed in the cover. As the cover is closed, the ridge engages the top of the integrated circuit device received within the socket. The distance the body of the integrated circuit device is moved will depend upon the distance the ridge extends from the cover body. As the IC body is engaged by the ridge, the ridge will serve as a fulcrum, in a sense, and the device will have some tendency to equalize pressure on the contacts and device leads.
This proposed solution, however, has a number of shortcomings. The ridge height is, typically, fixed. Consequently, this solution does not allow for variations in thickness of the device to be tested. As a result, devices having a thicker dimension will result in the deflection of contacts to a greater degree and a resultant higher force being exerted upon the contacts. This force can result in damage to the leads of the devices being tested. The larger deflection of the contacts also causes higher stress on structures employed for mounting the contacts. These factors, in turn, result in a shorter test cycle life.
This proposed solution also causes problems in that the leads are not always maintained to define a plane generally parallel to a plane defined by the contact array. When the cover is closed over the test socket housing, the angle formed between the device and the contact array is not always eliminated. As a result, lead damage and contact damage can occur.
It is to these dictates and problems of the prior art that the present invention is directed. It considers these dictates and problems, and results in a test socket construction which improves over structures and methods employed heretofore.